This invention relates to shutter structure which selectively closes the viewfinder path of photographic apparatus. More particularly, the invention provides camera shutter structure for closing the viewfinder path to prevent further exposure of an exposed but unprocessed film unit of the self-developing type.
Most camera designs, other than those of the single lens reflex type, do not require that the viewfinder path be closed at any time. In most cameras, the viewfinder path is separate from the optical image path and separate from the path of the film. This separation of the viewfinder path from the image path and from the film path is generally easy to attain in a camera employing small format film, while still locating the viewfinder window close to the taking lens as desired for accurate framing. In a single lens reflex camera, where the viewfinder path goes through the taking lens, structures are known for closing the viewfinder during the brief time the shutter is open. These structures prevent light from entering the viewfinder and passing through the open shutter to the film.
Further, cameras of the self-developing type conventionally locate the spread rollers, which initiate processing of an exposed film unit to fix a visible image, directly adjacent the image surface, which is the site at which the film is exposed. The film, accordingly, is advanced directly from the image surface to the spread rollers without subjecting it to further optical paths, either of the image or of the viewfinder. Hence, even though the film in a selfdeveloping camera is relatively large to provide a readily viewable image, there has heretofore been little need to close the viewfinder path in these cameras.
It is, however, known in the art --as U.S. Pat. Nos. 3,460,452 of E. H. Land and 3,537,370 of R. R. Wareham disclose-- to close both the image path and the viewfinder of a scanning-type self-developing camera. In the camera which these patents disclose, as a film unit moves under a scanning type exposure aperture, a leading portion of it crosses the viewfinder path. The film unit, however, picks up a flexible shade which shields it from unwanted exposure by light in the viewfinder. After scanned exposure of the entire film unit, the movement of the film unit is reversed and it is drawn back under the scanning aperture to be fed through the spread rollers. To avoid exposure during this second pass under the scanning aperture, a capping blade is interposed across the image path during the reverse film movement. Thus, in these cameras the opaque shade shields the exposed but unprocessed film during passage both forward and backward across the viewfinder path, and the capping blade shields it from the image aperture during the reverse movement.
The two film-shielding structures, i.e., the shade and the capping blade, are located separately in the camera and operate essentially independently of one another. Also, it is noteworthy that this prior scanning-type camera has the spread rollers close to the film package, and moves the film back and forth as described above by selective engagement with the rollers. Further, the camera has no shutter of the conventional type, i.e., which opens and closes to expose a stationary film unit.
Accordingly, it is an object of this invention to provide a selective viewfinder closure for a photographic camera and which operates automatically with the camera shutter. The term "viewfinder" is used herein in a broad sense to include a photographic range finder and even certain forms of photometer or other "electric eye" exposure-control sensors.
Another object of the invention is to provide a camera viewfinder closure for shielding unprocessed film and which operates with a single direction of film advance. A further object is that the viewfinder closure opens only after passage of the unidirectionally-advancing film.
A more specific object is to provide a camera viewfinder closure which closes without requiring engagement with the film. It is also an object, however, that the closure sense the film passage to control the re-opening of the viewfinder path.
Another object of the invention is to provide an improved photographic shutter which operates with electronic exposure control and which includes a viewfinder closure.
A further object of the invention is to provide shutter and viewfinder closure apparatus of the above character which is relatively easy to incorporate in a camera, is of relatively low cost manufacture, and operates reliably.
Other objects of the invention will in part be obvious and will in part appear hereinafter.